Forcing a User to Use SSL-Encrypted Pages

Here is a simple function to see if a user is connecting via SSL or not:

<?php
function is_SSL() {
    /* Checks to see whether the page is in secure mode */
    if ($_SERVER['SERVER_PORT'] == "443") { 
        return true;
    } else {
        return false;
    }
}
?>

This function works by checking the port through which the client connected to the server (SSL is port 443). If the access is not secure and it should be, you can use $_SERVER['PHP_SELF'] and the header() function to redirect to a secure version of the page.